It is standard practice to provide roadways with reflective markers embedded in the roadways to designate the separation between traffic lanes. It is normal practice to provide an intermittent white paint line between traffic lanes, each paint line being 10 feet long, separated from the next section of paint line by a distance of 30 feet. This unpainted portion is known as the "skip" line. The reflector is positioned exactly in the middle of the skip line, 15 feet from the ends of each 10 foot paint line. On main highways and straightaways the reflector is positioned in alternate skip lines. On curves and on rural roads the reflector is positioned on each skip line. In those portions of the United States that is subject to snowfall and consequent plowing by snowplows to remove the snow, it is necessary to protect the reflector from damage by the edge of the mold board of the snowplow. In the case of raised reflectors, a raised cast iron H-shaped unit in which the reflector is embedded has been developed for this purpose. An example of such a unit is the Stinsonite 96. This type of reflector and means for cutting a receptacle in the pavement to receive it is described in U.S. Pat. No. 4,463,989, Kennedy.
An alternative solution to this problem which is used in some jurisdictions is to provide a slot, usually about 43/4 inches wide, 5/8 inches deep, and 52 inches in length. This slot may be flat with rounded portions at each end for two-way traffic, each end housing a reflector which is attached to the bottom of the slot at each end by means of epoxy adhesive. In the case of one-way traffic, the slot quite frequently is sloping throughout the entire length of the slot down to a maximum depth near the end at which point a reflector is attached to the base by means of epoxy adhesive.
In cutting such slots it is desirable to have the surface speed of the cutting blades at an optimum amount. This speed will vary from 9,000 to 12,000 feet per minute depending upon the diameter of the blade and the pavement being cut. Blades used for this purpose have diamond cutting edges and are very expensive, costing about $1,200. In making a cut 43/4 inches wide, 16 or 17 blades must be ganged together. If the blades are operated at other than an optimum speed, the cutting edge will wear down at a much more rapid rate thus dramatically increasing the cost of operation. The surface speed of the blade and the transverse speed of the platform supporting the blade are manually controlled by the operator so that when varying densities of the material being cut are encountered the judgment of the operator is relied upon to slow the transverse movement of the platform or to modify the speed of the blade, or both, and, of course, the manner in which this is done will vary from operator to operator, depending upon their experience.
Solutions to this wear problem are described in greater detail in co-pending patent application Ser. No. 927,210, Kennedy, entitled Self-Regulating Concrete Cutting Saw.
The present invention relates to a portable, self-propelled machine which may be used to cut a slot in the surface of pavement, the shape and length of said slot being determined by rotating cams which guide the movement of the rotary cutting blades which are used to cut the slot. The cams, which are positioned on a common shaft connected to the shaft on which the rotary cutting blades are mounted, also serves to position the rotary cutting blades so that they always perform their cutting function while at right angles to the tangent to that portion of the surface of the pavement in which the slot is to be cut.
Furthermore, this invention embodies an automatic control mechanism which will reduce the speed of the motor propelling the device so that the rotating cutting blades are always operated at maximum efficiency.
It is therefore an object of this invention to provide a self-propelled device for cutting a slot in the surface of the pavement in which the shape and length of said slot is determined by a plurality of cams attached to the cutting blades.
It is another object of this invention to provide such a device in which the cams also function to insure that the rotary cutting means performs its cutting function while at right angles to the tangent to that portion of the surface of pavement in which the slot is to be cut.
It is still another object of this invention to provide a self-propelled pavement slot cutting machine in which the longitudinal movement of the cutting blades through the pavement will vary, depending upon the density of the pavement encountered with the rotational speed of the blades being maintained essentially constant.
These, together with other objects and advantages of the invention will become more readily apparent to those skilled in the art when the following general statements and descriptions are read in the light of the appended drawings.